On the increase in the concentration of primordial black holes in the halos of dwarf galaxies

TL;DR

Numerical experiments show primordial black holes can concentrate in dwarf galaxy halos, leading to new constraints on their abundance based on stellar cluster heating observations.

Contribution

This study introduces a novel numerical approach that accounts for early dark matter formation and halo non-stationarity to predict PBH concentration in dwarf galaxy halos.

Findings

PBHs can concentrate in dwarf galaxy halos exceeding 1% local fraction.

Constraints on PBH abundance are two orders of magnitude stricter than previous estimates.

Results impact models of stellar cluster heating in dwarf galaxies.

Abstract

Through numerical experiments, we have predicted that if dark matter (DM) contains even a small fraction, $f_0\sim10^{-4}$, of primordial black holes (PBHs), during the formation of the gravitationally bound halo of a dwarf galaxy, these PBHs will concentrate in a region with a radius of about 10 pc, so that their local fraction will exceed 1%. Unlike previous studies of PBH migration to the centers of galaxies, the numerical experiments conducted here take into account the early formation of a massive "dress" of DM around the PBHs and the non-stationarity of the halo during its formation. Applying our results to models of heating stellar clusters in the Eridanus II and Segue I galaxies due to dynamical friction between stars and PBHs allows us to impose constraints on the abundance of PBHs that are two orders of magnitude stricter than previously thought.